1. Field of the Invention
The present invention relates to communication methods and communication systems each using wireless tags and reader/writers.
2. Description of the Related Art
Communication systems that include wireless tags (also referred to as ID tags, ID cards, IC cards, IC tags, IC chips, radio frequency identification (RFID) tags, RF tags, wireless chips, or electronic tags) and reader/writers, and perform non-contact communication between the wireless tags and the reader/writers are widely used. Such a communication system performs communication by performing more than once a step of transmitting a response from a wireless tag to a reader/writer after the reader/writer transmits a command to the wireless tag and the wireless tag receives the command (for example, see FIG. 2 and the description of FIG. 2 in Patent Document 1). Repetition of this step is hereinafter also referred to as a command sequence.
Further, wireless tags that generate power supply voltage used for operating internal circuits with the use of electromagnetic waves from reader/writers (hereinafter also referred to as passive wireless tags) are widely used as wireless tags. Passive wireless tags themselves do not need to have power sources such as batteries, and can be made small.